Historian and biographer Helen Fry[1] observes that "the reputation of the London Cage will endure—and not for the justice that it secured against the evil Nazi perpetrators of mass murder. The rumors surrounding it will forever cast a shadow on British intelligence" (221). In the present book, she illuminates the darker corners behind the Victorian façades of Nos. 6, 7, 8, and 8a of Kensington Palace Garden during and immediately after World War II. The official files of the London Cage were not released to the National Archives until the 1990s, except for missing files (suspiciously) said to have been lost to asbestos contamination and floodwater damage.

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The London Cage comprises sixteen chapters and an epilogue, enhanced by photographs and illustrations of the facility, prisoners, interrogators, and notable staff members. The story extends from the desperate phase of Britain's early war years through to the postwar efforts to extract information relevant to the prosecution of German war criminals.

The central figure at the Cage, one of nine POW interrogation facilities, was Col. Alexander Scotland, who set the rules and methods for the work done there. Scotland's memoirs (sanitized by MI5) were published in 1957, but, as Fry notes, even the declassified, unredacted manuscript shows that Scotland withheld details of the treatment of German POWs.

Scotland was a strong personality and a ruthless interrogator. His service in the German army in Southwest Africa in 1904–7 (he spoke German, Spanish, Dutch, and Afrikaans) gave him keen insights into the culture of German soldiery. He himself had been imprisoned and interrogated as a spy by the Germans and in turn interrogated German prisoners in the Great War. The story of the London Cage would be very different, Fry notes, without him:

It was largely due to Colonel Scotland's expertise that by the end of the Second World War British intelligence had an impressive and adaptable interrogation policy that produced intelligence of the highest quality, unequalled in any other country. It was because of this that in February 1946 he was decorated with the American Bronze Star by Major-General William Biddle. (24–35)

Fry distinguishes interrogation methods used to extract intelligence useful in conducting the war from those designed to determine whether a prisoner had committed war crimes. She observes that abuses (alleged or actual) of recalcitrant prisoners did not always produce the best intelligence. Captain Denys Felkin observed that "the essence of interrogation is the honest reporting of unprompted statements by the prisoner" (61). Seemingly trivial mentions of factories or munition works could be pieced together into an increasingly coherent picture:

The value of this kind of information gathered from prisoners of war cannot be underestimated. From them, British intelligence could map a comprehensive understanding of the Nazi military capability and see that the pace of rearmament showed no sign of slowing down. These prisoners were interrogated a year before the invasion of Europe by the Allies on 6 June 1944. But in 1943, the Allies were already planning for D-Day, and intelligence such as this was used in military planning and strategic bombing raids on the German industrial heartlands …. Copies of these interrogation reports were distributed among the key [British] intelligence agencies … and American intelligence in Washington. (61)

On the other hand, life in the Cage became memorably unpleasant for unforthcoming prisoners—Scotland "appears to have been determined to extract the secret by whatever means necessary" (65). These means might include forcing prisoners to stand or run for hours on end in the paddock area of the Cage or to endure sleep deprivation. Despite prisoners' claims otherwise, Scotland denied that physical violence was ever used in interrogations in the Cage. Inquiries into prisoners' allegations were never conclusive. Scotland himself admitted only to the occasional regimental box-on-the-ears delivered to undisciplined or arrogant inmates. One spoke of sixty punches with a clenched fist!

Scotland may have believed that it was acceptable to apply moderate physical force to discipline a prisoner, but not to obtain military information. He wrote: "Nazi prisoners expected to be beaten up; after all, they were past masters in the practice … but this occurred only in one instance at the cage and that was after the war." Predictably, this was edited out of the final version of his manuscript by MI5 and the War Office. (67)

Equally predictably, after the war the British intelligence establishment was far more concerned about public perceptions of the Cage. After all, in the fevered atmosphere of 1939–45, interrogation practices were chiefly a product of Britain's struggle simply to survive and ultimately elicited high-value intelligence. The ends justified the means, even if abusive methods were visited upon relatively harmless inmates as well as hardened Nazis.

After D-Day, the Cage's mandate shifted to gathering evidence for use at war crimes trials. This entailed a new approach to interrogation and a new staff comprised in part of non-commissioned personnel familiar with German language, law, and customs; these included German-Jewish émigrés, many of whom had been interned on the Isle of Man and in camps around Britain before swearing allegiance to George IV and serving in British uniforms as "the king's most loyal enemy aliens." These interrogators had gleaned intelligence of immediate military value during the war and then helped investigate war crimes perpetrated against Allied soldiers, airmen, and special forces. The London Cage was the most important center outside Germany for dealing with high-profile Nazi war criminals, processing 3,573 prisoners in 1945–48. These included monsters like high-ranking SS men Sepp Dietrich, Kurt Meyer, and Reinhold Bruchardt, as well as military commanders like Albert Kesselring, Erich von Manstein, Walther von Brauchitsch, Hermann Ramcke, and Gerd von Rundstedt (113–25).

As with many prisoners interrogated during the war, inadvertently revealed information was often critical:

Once suspected war criminals were in the London Cage, an effective tactic was to place a particular prisoner in solitary confinement in a room next to another carefully chosen prisoner. The men would soon discover that the flues from the fireplaces in their room merged further up, allowing them to have a conversation. An eyewitness recalled: "They chatted up the chimney to each other. They thought they were so clever, they gave away all kinds of information because we had placed bugging devices in the chimney and were able to record their conversations." (127)

For decades since its closure in 1948, the Cage remained a sensitive subject owing to its (actual or suspected) methods of inducing less obliging inmates to talk, in part because no files for the period 1939–43 have been declassified. The London Cage thus makes a valuable contribution to our knowledge of intelligence gathering during and after the Second World War.

It also squarely confronts the question of what is morally permissible in defending civilization against the assaults of its most barbarous enemies. The author concludes that it remains unclear "whether the London Cage was guilty of its own war crimes" (220) and that "the darker side of mistreatment and torture appears to have risen in the postwar period, when the cage dealt with hated Nazi war criminals" (207). Colonel Scotland did not believe Geneva Convention protections extended beyond POWs to civilian prisoners or to war criminals in the military (207–8). We may well imagine his and his charges' feelings about fanatics guilty of inhumanity and genocide unprecedented in scale. Nor would the leadership of British intelligence have welcomed any suggestion of mistreatment that might have led to the overturning of war criminals' convictions. Still, as Helen Fry rightly concludes, the intelligence leadership knew better than anyone that "torture and brutality do not produce a cooperative prisoner; they serve only to make the prisoner tell you what you want to hear" (221).

[1] She is the author of over twenty books, including The M Room: Secret Listeners who Bugged the Nazis in WW2 (London: Marranos Pr, 2012), Spymaster: The Secret Life of Kendrick (id., 2014), and Churchill's German Army: The Germans Who Fought for Britain in World War II (2010; rpt. London: Thistle, 2015).